1. Field of the Invention
The present invention relates to the field of switched telephony, and more particularly, to a method and system for providing a telephone routing service that restores a calling number in a call that has been processed by a non-network service provider and rerouted to an alternate destination.
2. Background of the Invention
Many Advanced Intelligence Network (AIN) telephone services use the capabilities of a service node (also referred to as a service circuit node) for intelligent call routing. In a typical routing scheme, the service node (SN) accepts an incoming call, executes service-related logic, places an outgoing call in accordance with the service logic, and terminates the incoming call to the outgoing call to complete the connection. Usually, the destination of the outgoing call is a telephone number different from the original called number.
AIN networks use a complex, high speed, high traffic volume data packet-switched messaging system to provide versatility in the handling of telephone calls. The Advanced Intelligent Network System is described in U.S. Pat. No. 5,701,301 and U.S. Pat. No. 5,838,774, which are hereby incorporated by reference in their entirety.
The AIN enables telecommunications call control and database access from any computer or switching system connected to the Signaling System 7 (SS7) network. The Signaling System 7 network refers to the current implementation of the common channeling interoffice signaling control network used in the United States. The Advanced Intelligent Network (AIN) is a standard call control protocol that uses the SS7 network for message transport.
AIN infrastructures of the public switched telephone network include service switching points (SSPs), service nodes, signaling transfer points (STPs), and service control points (SCPs) with databases. The service control point is a computer that holds, accesses, and maintains one or more databases, performs service logic, and communicates with service switching points in directing call routing. Databases typically store subscriber-specific information used by the network to route calls. The service switching point communicates with the service control point and queries the service control point for subscriber-specific or network-specific instructions as to how calls should be completed. The signaling transfer point is a packet switch that shuttles signaling messages between AIN network elements. The service node is a computer system that can perform service logic, can communicate with parties via voice circuits, and can assess incoming call information and make appropriate connections. In most implementations of a public switched telephone network, service control points and service switching points are provided in redundant mated pairs to ensure network reliability. Also, typically, service control points are within a network, while service nodes typically can be within or outside of a network.
Much of the intelligence and the basis for many of the new enhanced features of the network reside in the local service control point. As known by those skilled in the art, service control points are physically implemented by relatively powerful fault tolerant computers. Typical implementation devices include the Star Server FT Model 3200 and the Star Server FT Model 3300, both available from Lucent Technologies™. The architecture of these computers is based on Tandem Integrity S2 and Integrity S1 platforms, respectively.
The service control points maintain the network databases used in providing custom services, such as databases that identify customers requiring particular services. To keep the processing of data and calls as simple and as generic as possible at switches, triggers are defined at the switches for each call. Triggers may be assigned to a particular subscriber line or call, and prompts a query to a service control point. The service control point then checks its database to determine how to route the call and whether a customized calling feature or custom service should be implemented for this particular call. The results of the data base inquiry are sent back to the switch from the service control point. The return message includes instructions to the switch as to how to process the call. The instruction may be to take some special action as a result of a customized calling service or custom feature. If a “continue” message is received at the switch from the service control point, the switch moves through its call states, selects the call digits, and may generate further messages that will be used to set up and route the call, as described above.
FIG. 1 illustrates a typical AIN architecture that uses the call processing, routing, and connection capabilities of a service node to provide a call forwarding service. For a typical terminating service, caller 100 places a call (call 1) to a subscriber's telephone number, which flows through the caller's service switching point 102 and hits a trigger on the subscriber's service switching point 104. The trigger initiates a query (query 1) to a service control point 112 through a signaling transfer point 110. In response to query 1, service control point 112 returns response 1, directing service switching point 104 to forward call 1 to service node 116 that provides the call forwarding processing. Service switching point 104 forwards call 1 to service node 116 through service switching point 106. When it receives incoming call 1, service node 116 identifies the subscriber by the called number of call 1 and looks up the subscriber's desired forwarding, destination in a database. Service node 116 then places an outgoing call (call 2) to that forwarding destination (through service switching points 106 and 108) and, when answered at the subscriber's forwarding destination 118, terminates the incoming call 1 to the outgoing call 2 to complete the call connection.
Because, according to current network signaling capabilities, service node 116 places outgoing call 2 to complete the connection, the calling number of outgoing call 2 is the telephone number associated with the trunk group of service node 116. Thus, to the subscriber's forwarding destination 118, call 2 appears to originate from service node 116, instead of caller 100. This drawback of the service node function negates telephone services and call processing functions that may need to know the identity of the caller, such as caller identification (“caller ID”).
This drawback is further compounded when service node 116 is outside a local exchange carrier's local access transport area (LATA—hereinafter referred to as “the network”) and call 1 contains private call information. In such a situation, the local exchange carrier is prohibited by federal regulation to forward private call information to service node 116. Thus, a local exchange carrier cannot manipulate dialing strings to pass the private call information through service node 116 to subscriber's forwarding destination 118. This additional drawback is quite significant when considering the large number of telephone services supported by non-LEC telephone service providers, which are typically referred to as enhanced service providers (ESPs).
Supported by an out-of-network service node, an enhanced service provider, also known as an information provider, is an unregulated (by the Federal Communications Commission) vendor that adds value to telephone lines using software and hardware external to the network of a local exchange carrier. The enhanced service provider supplements a local exchange carrier's standard offerings, supporting advanced call features such as voicemail, flexible call forwarding, single number service, call screening service (e.g., routing or blocking telephone calls based on the calling party), announcement service, or database processing (e.g., a database that provides the latest airline fares). These enhanced services are offered over common carrier transmission facilities used in interstate communications, which employ computer processing applications that act on the format, content, code, protocol or similar aspects of the subscriber's transmitted information; provide the subscriber additional, different or restructured information; or involve subscriber interaction with stored information. In other words, these enhanced services are computer processing applications that manipulate in some way the information transmitted over the telephone lines.
For example, with a flexible call forwarding telephone service, a service node receives from a calling party an incoming call to the called party (subscriber). In response, the service node determines the forwarding destination, determines how to route the call (including, for example, which outgoing port to use), sets up appropriate billing and call identity information, places an outgoing call to the forwarding destination, connects the incoming call to the outgoing call, and drops out to leave the calls connected at the service switching point to save the resources of the service node.
For single number service, a service node receives an incoming call, consults a database to determine a group of phone numbers to simultaneously ring, places outgoing calls to each phone number in the group, and connects the incoming call to the outgoing call that is first answered. Like flexible call forwarding, once the incoming and outgoing calls are connected, the service node drops out resulting in a single call via the public switched telephone network.
To execute these services, a call to a subscriber of an enhanced service is re-directed from the subscriber's telephone number to a service node in communication with the enhanced service provider, and once the service node completes the call processing, to an alternate destination dictated by the enhanced service. As described above, because a service node completes the connection to the forwarding destination, the original calling number of the caller is replaced by the service node number. Further, because the service node in communication with the enhanced service provider is outside of the local exchange carrier's network and because the enhanced service provider is unregulated, the local exchange carrier cannot forward private call information to the enhanced service provider for insertion into the outgoing call from the service node to the forwarding destination.